Coil structure



March 18, 1969 R. s. z|E| Es 3,434,088

COIL STRUCTURE Filed Oct. 17, 1967 F/G.-/ 4g 7 big/Z /0 I mus/v70? E. S.Z/ELES 4 7' TOR/VE V United States Patent 3,434,088 COIL STRUCTURERobert S. Zieles, Indianapolis, Ind., asslgnor to Bell TelephoneLaboratories, Incorporated, Murray Hill, Berkeley Heights, N.J., acorporation of New York Filed Oct. 17, 1967, Ser. No. 675,909 US. Cl.336-192 8 Claims Int. Cl. H01f /10, 27/28 ABSTRACT OF THE DISCLOSURE Acoil structure comprises a coil wrapped around a spool that isaccommodated by a cup-shaped frame. A flange on the spool has a pair ofbifurcated extensions about which the initial and final turns of thecoil are respectively wound, and one or more of these turns areultrasonically welded to rivets mounted in the base of the frame.

Field of invention This invention relates to the field of electricalcomponents and within that field to electrical coils. Furthermore, thisinvention while not limited thereto is particularly adapted forminiaturization.

Background of the invention With the development of solid state devices,miniaturization of electrical components has taken on a new impetus andeven though integrated circuits are now coming into commercial use,there still exists a need for miniature coils. Such coils are employedin miniature relays, inductors, transducers, and so on.

One of the major problems in the manufacture of miniature coils has beenproviding terminations for the coils. The coils are wound with fine wirethat is easily broken and therefore this Wire cannot itself be used forconnecting the coil into the circuit in which it is to be employed.Rather the fine wire of the coil must be electrically connected toheavier lead wires or terminals which are then used to connect the coilto the circuit.

The problem consists of providing a coil structure that permits theelectrical connection between the wire of the coil and the lead wires orterminals to be made using production line techniques.

Summary of the invention A coil structure is herein disclosed thatprovides a solution to the above problem. The coil structure comprises aspool having a flange at one end thereof that includes a pair ofbifurcated extensions, the extensions having a particular spatialrelationship with respect to one another. The initial turns of the coilare Wrapped around one of the extensions and the final turns of the coilare wrapped around the other of the extensions, one or more of the turnsin each case spanning the space between the bifurcations.

T-he spool is positioned on a base that has a pair of holes therein, theholes having the same spatial relationship with respect to one anotherthat the bifurcated extensions have to one another, and a rivet that hasa solid top and hollow bottom is mounted in each hole. The spool ispositioned on the base so that the wire-wrapped bifurcated extensionsare in juxtaposition with the tops of the rivets, and one or more of theturns of wire wrapped around the extensions are ultrasonically welded tothe rivets. The termination of the coil structure is completed by thesoldering of a lead wire to the hollow underside of each rivet.

3,434,088 Patented Mar. 18, 1969 "ice Description of the drawingDetailed description Referring to FIGS. 1 and 2 of the drawings, thecoil structure of this invention includes a spool 10 comprising atubular hub 12 and a single flange 14 at one end of the hub. The flange14 includes a pair of bifurcated extensions 15 that have a particularspatial relationship to one another, the bifurcated extensions in theembodiment shown in the drawing being diametrically opposed to oneanother.

A coil 16 is wrapped around the spool 10, the initial turns of the coilbeing wound around one of the bifurcated extensions 15, the body of thecoil being wound around the hub 12, and the final turns of the coilbeing wound around the other bifurcated extension. One or more of theturns wound on each bifurcated extension 15 span the space between thebifurcations, and to keep the turns from spilling off they areadvantageously coated with a thin layer of cement. As an alternative,wire coated with an adhesive insulation is employed, and eitherimmediately before or after wire is wound on the spool, the adhesivelayer is activated by solvent or heat to cause bonding between adjacentturns.

The spool 10 with the coil 16 thereon is accommodated by a dielectriccup-shaped frame 18 comprising a planar base 20 and a cylindrical rim22. The base 20 has a central hole 24 and a pair of lateral holes 25, acircular recess 26 encompassing each of the lateral holes. The lateralholes 25 have the same spatial relationship with respect to one anotherthat the bifurcated extensions 15 of the spool 10 have to one another.

Each lateral hole 25 and the recess 26 therearound accommodates anelectrically conducting rivet 28. Each rivet 28 has a solid head 30 anda tubular shank 32, and each rivet is positioned in a hole 25 with thehead in the recess 26 and the shank extending through the hole. Therivets 28 are secured in place by swaging the tubular shanks 32 onto theunderside of the base 20, and when so secured the tops of the heads 30are substantially flush with the nonrecessed upper surface of the base.

The spool 10 with the coil 16 thereon is positioned with the flange 14on the upper surface of the base 20, with the hub 12 overlying thecentral aperture 24 in the base and with one or more of the turnswrapped around the bifurcated extensions 15 overlying the heads 30 ofthe rivets 28. The spool 10 and the base 20 advantageously includemeans, such as locating studs on one and receiving holes in .the other,for providing this orientation automatically.

One or more of the turns of wire wrapped around each bifurcatedextension 15 are ultrasonically welded to the head 30 of the rivet 28therebeneath. The tip of the ultrasonic welding toolis applied to one ormore of the turns of wire at the point that they extend between thebifurcations, the tip pressing the wire against the head 30 of the rivet28. Ultrasonic energy is then applied to the welding tip and theactivated tip strips the insulation from the wire, removes theoxide'from the head 30, and bonds the wire to the head all in oneoperation.

Termination of the coil structure is completed with the soldering of alead wire 34 to the underside of each rivet 28. Since the shank 32 ofeach rivet 28 is tubular, the underside of the rivet has a cavitytherein. This cavity accommodates the end of a lead wire 34 and therebyfacilitates the soldering of the lead wire to the rivet 28. Soldering ofthe lead wires 34 to the rivets 28 is possible because the ultrasonicwelding of the coil wires to the rivets provides a metallurgical bondthat is not disturbed by the heat generated in the soldering operation.

The cup-shaped frame 18 serves as an enclosure for the coil 16 and ifdesired the coil can be potted therein. In addition, since the hub 12 ofthe spool is in registration with the central opening 24 in the frame18, a core or pole piece can be readily inserted into the hub. Thus thecoil structure is readily adaptable to a number of different uses.

What is claimed is:

1. A coil structure comprising:

a base having a planar surface in which a pair of spaced holes areformed, the holes having a particular spatial relationship with respectto one another;

an individual electrically conducting rivet mounted in each hole in thebase;

a spool having a flange at one end thereof that includes a pair ofbifurcated extensions, the bifurcated extensions having the same spatialrelationship with respect to one another that the holes in the base haveto one another; and

a wire coil wound around the spool, the initial turns of the coil beingwound around one of the bifurcated extensions and the final turns of thecoil being wound around the other bifurcated extension, the turns beingwound so that at least one spans the space between the bifurcations;

the wound spool being positioned on the base with the bifurcatedextensions overlying the rivets and one or more of the turns of wireextending between the bifurcations of each extension being electricallyconnected to the top of the rivet therebeneath.

2. A coil structure as in claim 1 wherein the base is formed from adielectric material.

3. A coil structure as in claim 1 further including a lead wireelectrically connected to the underside of each rivet.

4. A coil structure as in claim 1 wherein the base includes a recessthat encompasses each hole, the recess about each hole being of a sizeto accommodate the head of the rivet positioned in the hole and being ofa depth so that the top of the rivet is substantially flush with thenonrecessed surface of the base.

5. A coil structure as in claim -1 wherein one or more of the turns ofwire extending between the bifurcations of each extension areultrasonically welded to the rivets therebeneath.

6. A coil structure as in claim 1 wherein the base is part of acup-shaped frame that accommodates the wound spool.

7. A coil structure as in claim 2 wherein the lower ends of the rivetsare tubular and thereby permit soldering of the lead wires therein.

8. A coil structure comprising:

a dielectric base having a planar surface in which a pair of spacedholes are formed, the holes having a particular spatial relationshipwith respect to one another, the base further having a recess thatencompasses each hole;

an individual electrically conducted rivet mounted in each hole in thebase, the head of each rivet being accommodated by the recessencompassing the hole, and the top of the rivet being substantiallyflush with the nonrecessed surface of the base;

a spool having a flange at one end thereof that includes a pair ofbifurcated extensions, the bifurcated extensions having the same spatialrelationship with respect to one another that the holes in the base haveto one another; and

a wire coil wound around the spool, the initial turns of the coil beingwound about one of the bifurcated extensions and the final turns of thecoil being wound about the other bifurcated extension, one or more ofthe turns being wound so that they span the space between thebifurcations.

the wound spool being positioned on the base with the bifurcatedextensions overlying the rivets and one or more of the turnsof wirebetween the bifurcations of each extension being ultrasonically weldedto the top of the rivet therebeneath.

References Cited UNITED STATES PATENTS 3,007,125 10/1961 Furbee 336-192X 3,271,760 9/1966 Sloan.

LEWIS H. MYERS, Primary Examiner.

E. GOLDBERG, Assistant Examiner.

US. Cl. X.R. 3 36208

